The use of binding assays on a solid phase is a common approach to measuring the levels of analytes in a sample. There are many types of natural and synthetic binding reagents (for example, antibodies, nucleic acids, aptamers, receptors, ligands, etc.), solid phases (e.g., the surface of a container or well or the surface of a microparticle) and assay formats (direct binding, sandwich, competitive, etc.) that are known in the art of solid phase binding assays. One specific example that illustrates the types of processing steps that are typical for a solid phase binding assay is a sandwich immunoassay which uses two antibodies directed against the target analyte, one of which is immobilized on a solid phase and the other carrying a label that is detectable through some detection technique (e.g., using fluorescence, chemiluminescence, electrochemiluminescence, absorbance, or the measurement of an enzymatic activity). When the solid phase is the surface of a well in a multi-well plate, typical steps in this format may include: (i) adding a sample to a well and incubating to allow analyte in the sample to be captured by the immobilized antibody in the well; (ii) adding the labeled detection antibody to the well and incubating so that the detection antibody binds to captured analyte to form a labeled “sandwich” complex on the solid phase and (iii) measuring the labels that are present in sandwich complexes on the solid phase.
Optionally, the wells may be washed before or after any of the steps to remove any unbound materials prior to addition of new solutions. During the incubation steps, the plates may be shaken to reduce the time and improve the reproducibility of the binding reactions. One exemplary detection technology that may be used to measure labels during the measuring step is electrochemiluminescence (ECL) detection, which employs labels such as derivatives of ruthenium tris-bipyridine that emit light when in proximity to oxidizing or reducing electrodes under appropriate chemical conditions (see, e.g., U.S. Pat. No. 6,808,939 which is incorporated herein by reference in its entirety). Instrumentation and consumables that are designed to carry out binding assays in multi-well format with ECL detection have been described (see, e.g., U.S. Pat. No. 7,842,246 which is incorporated herein by reference in its entirety). The '246 patent describes multi-well consumables having integrated electrodes within the well that are used as solid phase supports for antibodies or arrays of antibodies. The formation of labeled complexes on the electrodes is measured by applying a voltage to the electrodes and measuring the resultant ECL signal. An ECL read buffer, such as a buffer containing tripropylamine or another tertiary amine (see, e.g., U.S. Pat. No. 6,919,173 which is incorporated herein by reference in its entirety) may be added to the well prior to applying the voltage to provide chemical conditions that lead to efficient generation of ECL. A number of alternative protocols for carrying out ECL assays have also been described including protocols with an additional step during which capture antibodies are immobilized from solution (see, e.g., US Published Patent Application No. 20140256588 which is incorporated herein by reference in its entirety) and protocols where the measurement step includes an amplification step prior to the ECL measurement (see, e.g., US Published Patent Application No. 20140272939 which is incorporated herein by reference in its entirety).
In certain situations, ECL electrodes or other solid phases may be treated with a material (a “blocker” or “blocking reagent”) that prevents non-specific binding of analytes or assay reagents. This treatment may be carried out as a separate “blocking” step or blocking reagents may be included in the buffers or diluents used during other steps of an assay procedure. Examples of useful blocking reagents include proteins (e.g., serum albumins and immunoglobins), nucleic acids, polyethylene oxides, polypropylene oxides, block copolymers of polyethylene oxide and polypropylene oxide, polyethylene imines and detergents or surfactants (e.g., classes of non-ionic detergents/surfactants known by the trade names of Brij, Triton, Tween, Thesit, Lubrol, Genapol, Pluronic, Tetronic, F108, and Span).
Heretofore, the steps in ECL immunoassays are completed by various individual machines. For example, the washing of the multi-well plates is accomplished by plate washing machines; the pipetting of samples and reagents into multi-well plates is carried out by mechanized pipetting machines having a large number of pipette tips; the stirring of the samples and antibodies is carried out by mechanical shakers; and the excitation of analyte-antibody complexes and sensing of the emitted light are conducted by plate reading machines. However, there remains a need in the art for an overall system that integrates all these individual machines into a single interconnected system that improves efficiency, provides the ability to clean multiple pipette tips during a run, and provides thermal control to satisfy the operating temperature ranges of the reagents and/or the samples.